Multi layer capacitor and apparatus for making same with roll cleaning means

ABSTRACT

The ceramic layer of multi-layered ceramic capacitors is provided by pressure rolling powders into sheets or films. A machine used to roll the powder utilizes a feed control roll disposed between and in working relationship between a stationary back-up roll and an adjustable compression roll.

United States Patent Fuller et al. Oct. 1, 1974 [54] MULTI LAYERCAPACITOR AND 2,693,154 11/1954 Appleton 425/367 APPARATUS FOR MAKINGSAME WI'III 3251 328 1g; :32; Morgan 5/36 X ROLL CLEANING MEANS3:060:502 0/1962 [76] Inventors: 'Fred J. Fuiler, 4446 S. Talman,3,339,233 9/1967 Chicago, Ill. 60632; John G, R26,665 9/1969 Powell425/79 Kirschner, 3320 Overland Pass, Northbrook, Ill. 60062; Richard A.Stark, 177 Drak L D Fl m Primary Examiner-Robert L. Spicer, Jr. lll.60016 Attorney, Agent, or Firm-Charles W. Hoffmann; 22 Filed: Dec. 10,1973 Robe" Meyer [21 Appl. No.: 425,273

i I Related US. Application Data ABSTRACT [62] D1v1s1on of Ser. No.302,029, Oct. 30, 1972.

[52] CL 325/230 425/79 425/l97 The ceramic layer of multi-layeredceramic capacitors 425/363 425/367 is provided by pressure rollingpowders into sheets or [51] Int. Cl. B29C 15/00 mm [58] Field of Search425/230, 335, 367, 363, A machine used to roll the powder utilizes afeed 425/115, 99, 223, 224 control roll disposed between and in workingrelationship between a stationary back-up roll and an [56] ReferencesCited adjustable compression roll.

UNITED STATES PATENTS 2,615,404 10/1952 Crosland et al 425/363 X 2Claims, 8 Drawing Figures PATENTEDHET H874 sneer 1 0; 4

FIG I 22 POWDER 20 FIG 2 FIG 5 TERMINATION MULTI LAYER CAPACITOR ANDAPPARATUS FOR MAKING SAME WITH ROLL CLEANING MEANS This is a division,of application Ser. No. 302,029, filed Oct. 30, I972.

This invention relates to multi-layered ceramic capacitors; and moreparticularly it relates to such a capacitor having powder rolled ceramiclayers and to a means and method of providing such layers.

Multi-layered miniature capacitors are used extensively in hybridintegrated circuits and microminiaturized printed circuits. Suchcapacitors provide higher capacitor values than those attained inmonolithic integrated circuits. In order to meet its intended uses, suchcapacitors should enclose a high electrical capacitance within a smallvolume and it should also be capable of simple and inexpensivemanufacture.

For the most part such capacitors have been made by a slip castingtechnique. While for the most part satisfactory, this technique issomewhat time consuming and expensive. In addition, capacitors made bythe slip casting process sometimes had pinholes such that there wasshort circuiting and dielectric failure.

The present invention is concerned with the making of multi-Iayeredceramic capacitors and has as one of its objects the provision of amulti-Iayered ceramic capacitor having substantially no pinholes orvoids in its structure.

Another object of the invention is the provision of a multi-layeredceramic capacitor wherein the ceramic layers are formed by powderrolling techniques.

Still another object of the invention is the provision of a powderrolling machine.

Yet another object of the invention is the provision of a powder rollingmachine capable of rolling ceramic powders into a very fine film.

Another object of the invention is the provision of a powder rollingmachine having a stationary back up roll and an adjustable compressionroll with a drive and feed control roll disposed between the stationaryand compression roll and in working relationship therewith.

These and other objects of the invention will become apparent from thefollowing description taken in conjunction with the accompanyingdrawings wherein:

FIG. 1 is an enlarged photograph of a partial section of a multi-layeredceramic capacitor;

FIG. 2 is a schematic showing a process step in forming multi-layeredceramic capacitors according to the invention;

FIG. 3 is a schematic showing another process step in forming thecapacitors;

FIG. 4 is a front elevation of a powder rolling machine;

FIG. 5 is a section taken along the line 5-5 FIG. 4;

FIG. 6 is a top view of a portion of the machine;

FIG. 7 is a transfer of FIG. 6; and

FIG. 8 is a perspective view of an element of the powder rollingmachine.

Generally speaking, the present invention is directed to a multi-layeredceramic capacitor comprising a body containing a plurality of alternatelayers of pressure rolled ceramic and metallic electrodes and outertermination layer portions electrically connecting alternate electrodelayers.

The multi-layered ceramic capacitor is fabricated by passing powders ofthe ceramic through a rolling machine to compact the powder into a verythin sheet or film, printing metallic electrodes on the sheet in apredetermined pattern, pressure bonding a predetermined number of thesheets together, trimming, if necessary, the sheets to a predeterminedsize. and then applying termination layers portions to ends of thesheets to electrically connect alternate electrode layers.

A powder rolling machine particularly adaptable to rolling the ceramicpowder into the required film, in general includes a stationary back uproll. an adjustable compression roll, a drive and feed control rolldisposed between the back-up and compression rolls and in workingrelationship therewith. and means supplying powder to a compacting areadefined by the compression roll and the drive and feed control roll.

Referring now to the drawings, and in particular FIG. 1, there is showna multi-layered ceramic capacitor, which in general comprises a body 10which is composed of ceramic layers 12 each separated by an innerelectrode layer 14. The electrodes 14 extend substantially over theinterface between adjacent ceramic layers. The inner electrode layersalternate in their extension to the oppositely opposed ends of theceramic layers and the alternate inner electrode layers are electri'cally connected by outer termination or electrode layer portions 16 and18 thus providing alternate polarity electrodes over substantially allof the ceramic layers therebetween. The outer termination layer portionsusually encase each end of the body as well as provide an electrodeportion for attachment into electrical circuitry. It should beunderstood that although three layers of ceramic and two layers ofelectrodes are shown, the invention need not be so limited and that anynumber of desired layers may be used.

The ceramic materials which can be employed include one or more ceramicconstituents, such as barium, calcium, lead and/or strontium titanatewith or without the addition of zirconates of the above mentioned andother metals and metallic oxidesJThese usually produce ceramics ofrelatively high dielectric constant generally desirable for relativelyhigh capacitance capacitors.

Metals which can be employed as electrodes and termination portionsinclude metallic conductors and their alloys. Preferably such metalsshould not deleteriously react or alloy with the constituents, such asthe metallic constituents, of the ceramic material. Typical metalsinclude high temperature metals and alloys which have melting points ator above the sintering temperature of the ceramic material such asrefractory metals i.e., tungsten, molybdenum and the like, and al loyscontaining such, and the noble metals such as palladium, platinum, goldand silver and alloys containing such.

According to a feature of the present invention, the ceramic layers 12are provided by pressure rolling ceramic powders into a thin sheet orfilm. It has been found that when the ceramic layers are so formed thatthere is substantially no failure of the dielectric or short circuiting.It is believed that such improved properties of the capacitor areachieved by virtue of the powder rolled material being relatively densewith substantially no pinholes" with a more uniform ceramic film.

Referring to FIGS. 2 and 3 there is shown schematically the processsteps for forming the multi-layered capacitor of FIG. 1 using powderrolled ceramic for layers 12. Powders of a suitable ceramic are fed topressure rolls 20, 22 and 24 with the powder being rolled primarilybetween rolls and 24, roll 22 being a back-up roll. The rolled powderemanates from the rolls as a very thin sheet or film 26. The innerelectrodes 14 are then printed on the film in a predetermined patternthrough a suitable printing applicator means 28. The electrodes may beapplied as a metallic paste or paint, for example. The sheets are thencut to a predetermined size and then, as shown in FIG. 3 are fed to apress means 32 to be bonded together to form a body 36 which is thentrimmed to a predetermined size 38 through cutting means 39. Asindicated, outer termination layer 16 and 18 (FIG. 1) are then appliedto complete the body 10 of FIG. 1. The application of the terminationlayers and electrical terminals for attachment into electrical circuitsmay be accomplished in a manner well known in the capacitor art and formno part of the present invention. For example, well known dippingtechniques may be used.

Referring now to FIGS. 4-8, there is shown a machine particularlyadaptable to rolling powders of ceramics, such as previously noted, intovery fine sheets or films. In general, the fine film is achieved througha three roll machine wherein a small center roll is used as the driveand feed roll with the powders being rolled between it and anotherlarger roll. A third larger roll serves as a backup roll and operatesagainst a side of the center roll opposite the other larger roll.

In FIGS. 4 and 6 there is shown a first pair of plates 40 and 42 carriedon a suitable base 44. A second pair of plates 46 and 48 are pivotallymounted on plates 40 and 42 through a pair of plates 50 coupled to ashaft 52, the shaft being rotatably mounted in plates 40 and 42.Rotatably journalled in plates 40 and 42 is a relatively large roll 54.A second large roll 56 is rotatably journalled in plates 46 and 48.Since roll 54 is carried by fixed plates 40 and 42 it is stationary asopposed to roll 56 which is movable, being carried by pivotally mountedplates 46 and 48.

A third center roll 58 of relatively smaller diameter is rotatablyjournalled in plates 40 and 42 and disposed in working relation betweenrolls 54 and 56. As shown in the illustrative embodiment, roll 58 servesas a drive and feed control roll. However, it should be understood thatthe invention need not be so limited and that either of the other rollsmay serve as the drive roll. Roll 58 is power driven through a suitablemotor, the roll being coupled to the motor through pinion 60 which isfixedly carried by the roll, worm gear 62 which is fixedly carried onshaft 64, shaft 64 being rotated by the motor through chain drive 66 andsuitable gear means disposed in housing 68. As shown, shaft 64 rotatesin bearings 70 and 72. Rotation of roll 58 causes rotation of rolls 54and 56; thus rolls 54 and 52 are driven by the center roll. As viewed inFIG. 7, center roll 58 is driven clockwise to drive rolls 54 and 56counterclockwise and clockwise respectively.

Powder to be rolled is fed to a compacting area 74 (FIG. 7). The powderis fed to a box-like screen which is vibrated by vibrator 78. Vibrator78 is carried on a frame 86 which includes sidewalls 88, 90, and 94,

the frame being fixedly held at one end to plates 40 and 6 42 through aplurality of bolts 96. The vibrator 78 is carried on the frame 86through plate 98, the vibrator being held on the plate through spring100. Screen 80 is vibrated by virtue of being attached to plate 98.

From the screen 80, the powder is fed through a compartment 81 formed byside walls 82, 84, 85, and 87. As shown in FIG. 7, wall 82 limits thepowder compartment area so to direct the powder away from the face ofroller 56 until the powder reaches an area between roller 58 and theroll 56. Or. more precisely. the powder is directed away from roll 56until it reaches the bite between rolls 56 and 58. Thus, the center roll58 is the feed roll. This aids in maintaining a "fine" feed control ofthe powder so that close tolerances can be achieved in rolling thepowder to a very fine sheet or film, for example .00] to .004 inches.

There is a blade 102 engaging roll 58 to maintain the roll free ofpowder. The blade is carried on a support 104 which is carried by plates40 and 42. Similarly, as indicated in FIG. 4, there are blades I06 and108 carried by plates 40, 42 and 46, 48 respectively to clean" rolls 54and 56 respectively.

A pair of micrometer adjusting means 110 provides for pivoting of theplates 46 and 48, thus permitting roll 56 to be adjusted. Eachmicrometer adjusting means 110 includes a pair of nuts 112 and 114, oneeach carried by the plates 40, 42 and 46, 48, and bolt 116 engaging thenuts. There is a thread differential between the two nuts so that amechanical advantage is achieved when plates 46, 48 are pivoted byturning handle lll.

Referring to FIG. 8, another feature of the machine is shown. As shownroll 58, blade 102 and its support frame 104, pinion 60, and supportblocks 116, 118, and are fabricated as a single unit to provide acartridge 115. Blocks 116 and 118 are adapted to be received by plates40 and 42. Notches 41 of the blocks of the blocks receive projections41' of the plates 40 and 42; while projections 43 engage notches 43' ofan L shaped frame 45. L-shaped frames 45 are secured to plates 40-42through bolts 47. The roll 58 can be easily replaced with a differentsize roll. When such replacement is made the positioning of roll 56needs to be adjusted to properly cooperate with the new roll. This canbe easily accomplished through the micrometer adjusting means 110.

In operation, powder is fed through screen 80 through compartment 81 tothe compacting area 74. The powder will be rolled between rolls 56 and58, roll 54 serving as a back up roll. Rolls 58 will serve as the driveroll driving rolls 56 and 58 through friction. Since there issubstantially no powder reaching roll 56 until an area at the bitebetween rolls 54 and 56, roll 58 will determine the rate of feed forbetter and close tolerances. The powder passing between the rolls willbe rolled into a thin sheet or film.

What is claimed is:

1. A powder rolling machine comprising:

a. a base.

b. a first pair of spaced upstanding plates carried by said base,

c. a first roll rotatably carried by said first pair of plates.

d. a second pair of spaced upstanding plates pivotally carried by saidfirst pair of plates,

e. coupling means connecting said first and second pair of plates in aspaced predetermined position,

f. a second roll rotatably carried by said second pair of plates inspaced relation to said first roll,

g. a cartridge carried by said first pair of plates. said cartridgeincluding a rotatably mounted feed control roll disposed between and inworking relation 5 to said first and second rolls. h. means supplyingpowder to a compacting area defined by said second roll and said feedcontrol roll,

1. A powder rolling machine comprising: a. a base, b. a first pair ofspaced upstanding plates carried by said base, c. a first roll rotatablycarried by said first pair of plates, d. a second pair of spacedupstanding plates pivotally carried by said first pair of plates, e.coupling means connecting said first and second pair of plates in aspaced predetermined position, f. a second roll rotatably carried bysaid second pair of plates in spaced relation to said first roll, g. acartridge carried by said first pair of plates, said cartridge includinga rotatably mounted feed control roll disposed between and in workingrelation to said first and second rolls, h. means supplying powder to acompacting area defined by said second roll and said feed control roll,i. means applying power driven rotation to said feed control roll and,j. said cartridge further including means cleaning said feed controlroll
 2. A powder rolling machine according to claim 1, wherein saidcleaning means comprises a blade carried by said blocks, and engagingsaid feed control roll.